BACKGROUND AND PURPOSE: Perceived injustice has been defined as an appraisal regarding the severity and irreparability of loss associated with pain, blame and a sense of unfairness. Recent findings have identified perceived injustice as an important risk factor for pain-related outcomes. Studies suggest that perceived injustice is associated with opioid prescription in patients with pain conditions. However, the mechanisms by which perceived injustice is linked to opioid prescription are not well understood. The primary objective of this study was to examine the potential mediating roles of pain intensity, depressive symptoms and pain behavior in the association between perceived injustice and opioid prescription among patients with chronic pain.METHODS: This cross-sectional study used a sample of 344 patients with chronic pain being treated at a tertiary pain treatment center. Participants completed measures of perceived injustice, pain intensity, depressive symptoms, pain behavior and opioid prescription. Bootstrapped multiple mediation analyses were used to examine the mediating role of patients' pain intensity, depressive symptoms and pain behavior in the association between perceived injustice and opioid prescription.RESULTS: Consistent with previous research, we found a significant association between perceived injustice and opioid prescription. Interestingly, results revealed that pain behavior was the only variable that mediated the association between perceived injustice and opioid prescription.CONCLUSION: This study was the first to examine the mechanisms by which perceived injustice is associated with opioid prescription in patients with chronic pain. We found that pain behavior, rather than pain intensity and depressive symptoms, mediated the association between perceived injustice and opioid prescription. Future research in this area should employ a longitudinal research design in order to arrive at clearer causal conclusions about the relationships between pain behavior, perceived injustice and opioid prescription.